1. Field of the Invention
Embodiments of the present invention generally relate to an anchor for use with an expandable tubular.
2. Description of the Related Art
In the drilling of oil and gas wells, a wellbore is formed using a drill bit disposed at a lower end of a drill string that is urged downwardly into the earth. After drilling to a predetermined depth or when circumstances dictate, the drill string and bit are removed and the wellbore is lined with a string of casing. An annulus is thereby formed between the string of casing and the formation. A cementing operation is then conducted in order to fill the annular area with cement. The combination of cement and casing strengthens the wellbore and facilitates the isolation of certain areas or zones behind the casing including those containing hydrocarbons. The drilling operation is typically performed in stages and a number of casing or liner strings may be run into the wellbore until the wellbore is at the desired depth and location.
The casing may become damaged over time due to corrosion, perforating operations, splitting, collar leaks, thread damage, or other damage. The damage may be to the extent that the casing no longer isolates the zone on the outside of the damaged portion. The damaged portion may cause significant damage to production fluid in the zones or inside the casing as downhole operations are performed. To repair the damaged portion, an expandable tubular patch may be run into the wellbore with an expansion cone. An anchor temporarily secures the patch to the casing. The expansion cone is then pulled through the patch using a hydraulic jack at the top of the patch. The hydraulic jack pulls the expansion cone through the patch and into engagement with the damaged casing. Thus, the patch covers and seals the damaged portion of the casing.
The hydraulic jack is limited in the amount of force it can apply to the expansion cone. Typical hydraulic jacks are limited to 35,000 kilopascal (kPa) applied to the work string. This limits the amount of expansion force applied to the expansion cone and thereby the patch. Further, the hydraulic jack requires a high pressure pump to operate which adds to the cost of the operation. Moreover, the work string must be sealed so pump pressure can be applied to operate the hydraulic jack which makes it difficult to pump fluid down to the expansion cone in order to lubricate the cone during expansion. Still further, the hydraulic jack has a very small and limited stroke. Thus, in order to expand a long patch, the hydraulic jack may need to be reset a number of times to at least anchor the patch to the casing.
Therefore, there exists a need for a mechanical expansion system capable of expanding a tubular with an increased force for an increased distance.